The specific aims of the study are to quantify heat shock protein 70 production in response to a single bout of intense heat stress; to determine the time coarse for heat shock protein production in response to a single bout of intense heat stress in humans; to determine the time delay between HSP70 mRNA upregulation and HSP70 production; to investigate potential differences in HSP levels between highly trained and sedentary subjects; and to investigate the potential ethnic differences in the human HSP response.